Question 673325
<pre>
23998

First put it in scientific notation

2.3998 × 10<sup>4</sup>

Draw a line after the 3rd digit from the left

2.39&#8402;98 × 10<sup>4</sup>

Since the digit just to the right of the &#8402; which is a 9,
is 5 or more we add 1 to the 9 just to the left of the &#8402; 
and since it becomes 10 we have to carry a 1 to the 3 making 
it 2.40. Eliminate the digits to the right of the &#8402;. 

2.40 × 10<sup>4</sup>

Important: Do not eliminate the 0 on the end of 2.40.  It is
nexessary to show the number of significant digits.

Answer: 2.40 × 10<sup>4</sup> 

Edwin</pre>